1. Field of the Invention
The present invention relates to magnetic recording medium, a magnetic storage and a method for reproducing information from the magnetic recording medium, suitable for high density recording, and, in particular, to a magnetic recording medium, a magnetic storage and a method for reproducing information from the magnetic recording medium in which the magnetic recording medium is selectively heated, and recording/reproduction is performed.
2. Description of the Related Art
Recently, high density recording has been rapidly promoted at a rate of 100% per year. In an in-plane recording method which is a main trend, it is presumed that the limit of plane recording density is 100 Gb/in2. The reason therefor is that, in a high density recording range, for the purpose of medium noise reduction, a size of a crystal grain which acts as a magnetization unit in a recording layer is reduced, and a zigzag in a magnetization transition zone which is a boundary between crystal grains is reduced. However, when the size of the crystal grain is reduced, a volume of the magnetization unit is reduced, and thereby residual magnetization is reduced due to thermal fluctuation. Thus thermal stability may deteriorate.
As a magnetic recording medium which satisfies both the medium noise reduction and the thermal stability, a magnetic recording medium (so-called synthetic ferrimagnetic medium) which has two magnetic layers which make exchange coupling therebetween antiferromagnetically has been proposed (for example, see Japanese Laid-open Patent Application No. 2001-056924). In this configuration, a substantial volume of a crystal grain corresponds to a sum of the two magnetic layers making exchange coupling, thereby thermal stability remarkably increases, and also, it becomes possible to further reduce the medium noise since it becomes possible to achieve microscopic crystal grains.